Sierra Designs Assailant Tent REVIEW

This four-season, one-person, single-wall tent is made of a fabric claimed to be more breathable than eVENT.

Overall Rating: Average

The Assailant is ergonomic and well designed for fast setup. However, it does not function well as a four-season tent, especially in snow and cold rain. Its DAC Featherlight poles and pole sleeves provide a strong structure, but the tent's profile holds snow on top of the tent and creates very unfavorable snow loads. The tent has four-way venting, but it does not perform adequately in snowy conditions. Its DriZone shell fabric is claimed to be highly breathable, but only performs well in warmer temperatures.

Introduction

When we saw Sierra Design's new Assailant tent at the Winter 2007 Outdoor Retailer Show, we were impressed by its design and breathability rating. The fabric is Sierra Designs' DriZone, which is a two-layer polyurethane laminate with a breathability rating of 28,000 g/m2/24 hr and waterproofness rating of 18,000 mm, which are outstanding numbers. The breathability rating is equivalent to that of eVENT fabric measured by the same test. How did the Assailant perform in our field tests, and how practical is a one-person tent for winter camping?

Performance

The Sierra Designs Assailant is a one-person, four-season, single-wall, freestanding tent made with waterproof/breathable fabric. It’s designed to provide all-weather shelter for one person plus gear. Many mountaineers prefer a tent of this type because it has a small footprint, is fast to set up, is very weather-resistant, and has room inside for gear.

Sierra Design’s DriZone fabric is a two-layer laminate with a ripstop nylon face fabric and a thick layer of polyurethane on the inside. All seams are taped. Their breathability claim for this fabric is extraordinary: 28,000 g/m2/24 hr (using the JIS 1099 test method). For comparison, three-layer eVENT, which is the undisputed (but tragically unavailable) standard for waterproof/breathable tent fabric, has a breathability rating of 27,826 by the same test. We don’t have any means to test those numbers, but we were curious to test the Assailant in the field to find out how well it performs.

Views of the Sierra Designs Assailant. It has a side entry (top left) with a half-moon shaped zippered door with a second mesh door behind it. The back view (top right) shows the Assailant’s three-pole design. There is a large vent at the bottom of the “V”. Each end (bottom left) has a smaller vent. The top view (bottom right) shows that it’s basically a triangle-shaped tent.

The Assailant uses one long diagonal pole plus two shorter extender poles. The DAC Featherlite NSL aluminum poles are pre-bent and easily inserted into pole sleeves that have a dead-end pocket at one end and grommet at the other. Setup is fast and simple; I timed it at 2.5 minutes. Eight stakes are required for a secure pitch, which includes two guylines on the ends.

The sleeping position is toward the front of the tent, where the length (with adequate headroom) is sufficient for a person up to about 6 feet 2 inches. However, tent height is only 30.5 inches, which makes this tent better suited for a shorter person. Extra floor space for gear and one mesh stow pocket are in the back of the tent.

Ventilation is via three vents (two on the ends and one on the back) plus the tent door, so the Assailant has 4-way ventilation. The vents have hold-open rods that are operated from the inside. There is no vestibule to protect the entry, but it is possible to open the top of the door about 4 inches without rain or snow entering the tent (assuming it’s not wind-blown).

Field Report

In my field testing, I was able to evaluate the Assailant in two snowstorms, an all-night rain, and cold temperatures down to 14 °F, but only minor winds.

With only 30.5 inches of headroom, the Assailant forced me to do everything while lying down. I could sit up in the center, but my head bulged the top of the tent. For me, the confinement was not my first choice for living conditions, especially on long winter nights.

The first snowstorm I experienced was just a couple of inches, but enough to point out one serious limitation of the Assailant - snow is held on top of the tent by the two pole sleeves. The second snowstorm I experienced in the Assailant at 9700 feet dropped a foot of snow overnight. It was a constant (and sleepless) process to heave the snow off the top of the tent from inside. The tent’s construction is quite strong to support snow, but there is a distinct risk of the tent suffering serious damage if it gets overloaded with snow, as it might if left set up all day in a snowstorm.

Two pole sleeves on top of the Assailant keep snow from sliding off. It didn’t take much snow to cover the rear and side vents.

In dry and warmer conditions, I kept all four vents (including the top of the door) open for nighttime ventilation, and the Assailant stayed dry inside. On really cold nights, with all vents open, I had some frost on the tent walls near my head (from my breathing) but the rest of the tent was dry. Overall, the Assailant performed well in dry conditions.

However, on one rainy night with a low of 38 °F, and during the snowy night described above with a low of 28 °F, I had copious amounts of condensation inside the tent. In both cases there was little air movement and not much of a humidity gradient, so the moisture could only condense on the cold tent walls. In cold temperatures, the tent’s small interior volume and the user’s close proximity to the tent walls contribute to the condensation problem. Unless there is good air circulation through the tent, moist air will contact the cold tent walls and condense or freeze.

The Assailant was a condensation chamber on a calm cool rainy night. Water dripped from wrinkles in the shell and the rear vent.

Assessment

As far as design and ergonomics, the Sierra Designs Assailant tent is well designed. It is easy to set up in locations with restricted space. Entry is from the side and there is sufficient room inside to accommodate one person plus gear. It’s made of high quality durable materials.

The DriZone fabric has a relatively thick polyurethane coating on the inside. Polyurethane is very durable so the coating stretches with the tent walls and won't be easily damaged with normal use. Obviously, there are limits to this durability.

Polyurethane's hydrophilic properties enable the DriZone fabric to transfer moisture effectively. Moisture is absorbed by the polyurethane, diffuses through the membrane, and then evaporates from the outside surface. Driven by vapor pressure gradients, it can be a slow process at lower temperatures because it involves two phase changes of water (vapor to liquid to vapor), and in no way compares with the ability of gas-permeable eVENT fabric to transport water vapor directly. Regardless of the claimed breathability specification for DriZone fabric, its performance in the field is not stellar. It does not appear to transfer moisture any faster than other polyurethane laminates. DriZone’s thick polyurethane coating does have the capacity to “bank” moisture as it is produced, up to a point, which will keep the interior of the tent dry for awhile.

A four-season tent should easily shed snow and ventilate well in wet conditions, but the Assailant is not designed well for snow. Pole sleeves on top of the tent hold the snow, and the shell does not have enough tautness and slope to shed snow, so it accumulates on the top of the tent and requires constant clearing to avoid overloading. All three vents are rather low and can easily be covered by snow, and there is no high vent except the door opening.

Furthermore, the tent does not manage moisture well. In dry weather it does just fine (like most tents do), but in wet weather moisture tends to stay inside creating heavy frost or condensation. The three vents have mesh in them which significantly restricts airflow, so it takes a pretty strong breeze to actually move air through the tent. The tent’s small stature exacerbates the condensation issue, i.e., the cold tent shell is close to the occupant, so condensation readily occurs and the occupant readily brushes against the wet walls.

These graphs show interior temperature, relative humidity, and dew point in the Sierra Designs Assailant on a clear cold calm night (left) and a rainy cool calm night (right). On the cold night, the relative humidity (purple line) inside the tent gradually climbed to 90+% because there was little air circulation to exhaust moisture. There was minimal condensation inside because the dew point temperature (yellow line) did not reach the air temperature (blue line). However, on the rainy cool night, the relative humidity maxed out at 100% most of the night, and the air temperature reached the dew point most of the night, a formula for copious condensation forming on the cold tent walls. (Data taken with a Kestrel model 4000 Pocket Weather Tracker)

The Assailant does not have a vestibule, so in wet weather wet gear must be brought inside the tent, which further exacerbates the moisture management issue in wet weather. Also, there is no overhang over the entry door to keep rain or snow from coming in, which would allow more effective use of the door for ventilation.

Im my opinion, a high-end breathable fabric single-wall tent should be shelled with a fabric that transfers moisture better than a polyurethane laminate. It should also have large weatherproof high vents to help exhaust moisture, and it should have a vestibule to stash wet gear. A PTFE or Epic shell would be better. Epic is lighter, but it also doesn’t transfer moisture very well at lower temperatures.

Finally, the Assailant at $319 is not a good value. For the same money and weight, you could have the Black Diamond Firstlight tent ($299), which provides 27.3 square feet of floor space and 42 inches of height, or the new Black Diamond HiLight ($339), which provides 27 square feet of floor space and is 40 inches high. Both tents pitch as tight as a drum, have steep walls that readily shed snow, and have an optional vestibule available. Closer in size to the Assailant is the Black Diamond OneShot tent ($290) which has 21.25 square feet of floor space, but is 36 inches high and will shed snow better than the Assailant. Admittedly the Black Diamond tents' Epic fabric is only water-resistant and will wet through after about 5 hours of rain, and Epic is not very breathable in cold temperatures. Alternatively, one could spend a few extra bucks to get the Integral Designs MK1 Lite, which has a PTFE fabric shell similar to eVENT.

Fascinating review Will, I had high hopes for this one. I would love a winter solo tent that offers a little more legroom than my ID MK1. Ah well. Another one out. Funny how so much "4-season" gear isn't, really.

Another tent bites the dust ( or snow) of real world testing
on 05/23/2007 21:18:21 MDT

It's a crime to have external poles for a 4 season singlewall tent and this review just makes that point obvious.

Besides providing less in the way of ledges for snow collection, internally mounted poles allow one to set up the tent from the inside (and take it down) in inclement weather. I betcha forces such as sudden wind gusts are better distributed with a sleeveless interior design over a greater area of the tent than with pole sleeves, as well.

I heart my internal pole Bibler and BD epic tents for Winter, general mtneering, and anywhere the wind blows hard and the snow falls deeply-----and in many other conditions, too.

Will,Thanks for the great review. Just looking at the pole design it is obvious that triangle of poles on the roof will collect snow like a bucket. What were they thinking? There are good reasons the two-pole tent dominates the market.Speaking of 2-pole tents, you mentioned a competitor for the Assailant, the BlackDiamond HiLight. I own one, and I must take exception to your statements about leaking and breathability. I spent a rainy night in one in temperatures hovering around freezing, and the epic fabric did not leak one drop. Condensation with two people in the tent was never more than a thin film of droppless moisture which could be felt with the bare hand. All other moisture vented out through the epic. In fact, eventually I zipped the vents closed to trap heat, and it still continued to vent. It is so air permeable in fact, I could feel wind coming through the fabric when the wind was really gusting. I do not think the paper thin epic fabric is durable enought to be called an expedition tent; but it is great for the UL hiker in occasional alpine/mountaineering conditions; and after reading this review; I must say, still a better choice than this SD Assailant. About $300, or get it at REI as I did for "free" if you know what I mean ;)

I have the assailant.Used it on Colorado Trail this year (hiked 26 miles/day av) it performed well and so I have grown fond of it. It sets up easy, makes little noise in gusty weather as fabic nice and taught, plenty long enough and never leaked in some heavy rain that lasted hours (a number of occassions). For a vestibule, I use a Integral Designs Sil Poncho. Fold it in half and secure loops on cape in the holes of pole sleeves. The width is ideal and it comes in yellow too. As for condensation, yes Ive experienced this. I find that if relative humidity less than about 85% in tent then thats fine. Above this and up to 100% I wipe the condensation off to stop it dripping on my sleeping bag.